Avalanche Forecast

Issued: Apr 5th, 2015 9:21AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Cornices and Wind Slabs.

ghelgeson, Avalanche Canada

Purcells.

Warmth remains the primary driver of avalanche hazard as we shift into a more spring like pattern. Minimize your exposure to large slopes if the snowpack is becoming moist or wet.

Summary

Confidence

Good

Weather Forecast

MONDAY: Freezing level starting at valley bottom, rising to 1500m. Light variable winds at all elevations. Trace of snow possible. Broken cloud cover.TUESDAY: Freezing level starting at 500m, rising to 1800m. Light variable winds at all elevations. No significant precipitation expected. Skies clearing in the afternoon.WEDNESDAY: Freezing level starting at 1000m, rising to 2000m. Light NE winds at all elevations. No significant precipitation expected. Clear skies initially, cloud cover building in the afternoon.

Avalanche Summary

Several cornice falls have been reported in the last few days, some of which have triggered avalanches on slopes below. On Wednesday, a rider triggered size 2 avalanche was reported that likely started on the March PWL before it stepped down to the ground.

Snowpack Summary

The recent 10 to 25cm of storm snow was shifted by variable strong winds into wind slabs on lee slopes above 2000m. Cornices are large and touchy in some spots. The new snow sits over a crust which is generally becoming more supportive. Low elevations sport an isothermal snowpack, which is now capped by a refrozen crust.Persistent weak layers in the upper snowpack remain a lingering concern, although they seem to be slowly gaining strength. In the north of the region, the mid-March crust/facet layer is down 40-60cm. The mid-February crust/facet/surface hoar layer, down about 80 cm, may also still be reactive in isolated areas. Weak layers which formed earlier in the winter are also a concern in certain spots.

Problems

Cornices

Large, vulnerable and dangerously heavy chunks of snow hang precariously over many ridge-lines. While cornice failure is problematic enough on its own, falling chunks of cornice also have the potential to release wind slabs on slopes below.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

Aspects: North, North East, East, South East, South, South West, West.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Recent winds have shifted snow into wind slabs in alpine terrain.

Use ridges or ribs to avoid areas of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 6th, 2015 2:00PM